Merge pull request #458 from pingcap/siddontang/fix-drop-table

fix drop table

stmt/stmts/drop.go

@@ -111,6 +111,8 @@ func (s *DropTableStmt) Exec(ctx context.Context) (rset.Recordset, error) {
 	var notExistTables []string
 	for _, ti := range s.TableIdents {
 		err := sessionctx.GetDomain(ctx).DDL().DropTable(ctx, ti.Full(ctx))
+		// TODO: we should return special error for table not exist, checking "not exist" is not enough,
+		// because some other errors may contain this error string too.
 		if err != nil && strings.HasSuffix(err.Error(), "not exist") {
 			notExistTables = append(notExistTables, ti.String())
 		} else if err != nil {

stmt/stmts/drop_test.go

@@ -57,6 +57,8 @@ func (s *testStmtSuite) TestDropTable(c *C) {
 	c.Assert(mf.Len(), Greater, 0)
 
 	mustExec(c, s.testDB, testSQL)
+	mustExec(c, s.testDB, "create table if not exists t (c int)")
+	mustExec(c, s.testDB, "drop table t")
 }
 
 func (s *testStmtSuite) TestDropIndex(c *C) {

structure/hash.go

@@ -140,7 +140,7 @@ func (t *TxStructure) HLen(key []byte) (int64, error) {
 func (t *TxStructure) HDel(key []byte, fields ...[]byte) error {
 	metaKey := t.encodeHashMetaKey(key)
 	meta, err := t.loadHashMeta(metaKey)
-	if err != nil {
+	if err != nil || meta.IsEmpty() {
 		return errors.Trace(err)
 	}
 

structure/structure_test.go

@@ -239,6 +239,9 @@ func (s *tesTxStructureSuite) TestHash(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(l, Equals, int64(0))
 
+	err = tx.HDel(key, []byte("fake_key"))
+	c.Assert(err, IsNil)
+
 	err = tx.Commit()
 	c.Assert(err, IsNil)